Multi-Channel WDM (De)Multiplexer Based on Multimode Contra-Directional Coupling Using Dielectric Etches

Abstract

we present a four-channel flat-top coarse wavelength-division multiplexing (CWDM) (de)multiplexer employing contra-directional coupling between multiple modes simultaneously with shallow-etched dielectric etches in a single multimode waveguide.

Ultra-Low Crosstalk and Fabrication-Tolerant Silicon-Nitride O-Band (de)Multiplexer Using Bragg Grating-Assisted Contra-Directional Coupler

“…In conventional WDM systems that use arrayed waveguide grating (AWG) [80]- [83], flattened responses are achieved via the double- image technique; however, this can lead to increased excess losses (ELs) of 2-5 dB [78], [84]. To flatten the filtering responses without compromising ELs, alternative devices based on different mechanisms have been employed [53], [57], [61], [63], [65]- [68], [70], [73]- [77], [79]. Although low-EL, flattop, and high-uniformity responses can be obtained using lattice filters based on Mach-Zehnder interferometers (MZIs), the XTs are usually larger than −15 dB because of the narrow splitting/coupling ratio bandwidths at the MZI coupling regions.…”

“…Another elegant approach to flattening responses is based on the Bragg grating structure (BGS) to achieve low-EL, highly uniform, and flat-top responses [53], [65], [66], [70], [77], [79]. A rectangular response was obtained in [65] with a sinusoidal-profile contra-directional coupling coefficient κ ac by using both amplitude and phase apodizations along the propagation direction.…”